[R] SVM linear kernel and SV

From: David Meyer <david.meyer_at_wu-wien.ac.at>
Date: Fri 13 May 2005 - 21:04:43 EST

> Thank you for your answer,
> but my problem concerns the support vectors. Indeed the two classes
> are well separated and the hyperplane is linear but the support
> vectors aren't aligned in parallel to the hyperplane. And according to
> me, the support vectors (for each class) should be aligned along the
> linear hyperplane and form the marge (by definition). But it's not the
> case. In fact, I'd like to understand why they are not aligned.

Remember the `cost'-penalty controlling for overlapping classes. It has some effect even in the linearly separable case causing more SVs than would actually be needed. Try adding e.g. `cost=1000' and you will obtain a result with only 2 SVs (why not 3? Because 2 SVs here solve the optimization problem. So in fact the hyperplane in this case is not uniquely defined, although only in a small range.)



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Fri May 13 21:08:35 2005

This archive was generated by hypermail 2.1.8 : Fri 03 Mar 2006 - 03:31:45 EST